2.13.7 HIV brain disease

How the virus reaches the brain

• In the Trojan horse route, HIV crosses the blood-brain barrier inside infected monocytes and T lymphocytes, often early in infection.

• Viral proteins such as gp120 and Tat, cytokines from infected macrophages and microglia, oxidative stress and excess glutamate signalling damage dendrites and synapses.

• HIV encephalitis shows multinucleated giant cells, microglial nodules and white matter pallor.

HIV-associated neurocognitive disorder

• HIV-associated neurocognitive disorder (HAND) is an insidious subcortical decline with mental slowing, retrieval-type memory loss, fine motor slowing and apathy.

• Suspect it when HIV risk exposure, such as injecting drug use, comes with weight loss or other systemic signs of immune suppression.

• Language and visuospatial function may be relatively preserved early.

• Exclude other causes, including depression, rather than attributing every low score to HIV.

Opportunistic brain disease

• Reactivated *Toxoplasma gondii* is the leading opportunistic central nervous system (CNS) pathogen in acquired immune deficiency syndrome (AIDS) and the commonest cause of focal lesions at a low CD4 count.

• Toxoplasmosis presents with fever, headache and focal signs, with multiple ring-enhancing lesions and oedema at the grey-white junction and basal ganglia.

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